Hulusimpang Formation.has known as Oligocene-Miocene rocks that consisted of volcanoclastic rock. Its scope was wide, especially in southern Sumatra. This formation is supposed as a prospect host of various hydrothermal mineralization. A preliminary study was carried out to examine the abundance of elements located in Way Kalianda River, Pesawaran, Lampung. This study was conducted by easuring its stratigraphy and analyzing its composition using an X-Ray fluorescence analyzer. The lithologies generally consist of lapilli tuffs, volcanic breccias, interbeded by claystone and sandstone; in addition, it is also frequently found petrified wood and andesitic-lithic fragments. As a result, the significant abundant elements are Fe (35.5%), Si (27.9%), Al (17.4%), K (6.7%), Cl (5.5%), Ti (1.7%), and Ca (1.5%) and also Mn, Ag, P, Mg, Sr, Zr, and Co. It also presents trace elements such as Rb, Zn, Pb, Te, V, Ba, Cr, Sn, Ni, Ga, Nb, Mo, and Eu. These elements are suggested from distal facies of intermediates-magma series Tertiary volcano.

<strong>Oxygen Consumption of Barred Loach Nemacheilus fasciatus (Valenciennes, 1846) under Different Stocking Densities</strong>. In aquaculture system, fish growth is affected by stocking densities. One way to predict the effect of stocking density on growth is to determine fish metabolic rate through oxygen consumption measurements. In Barred loach Nemacheilus fasciatus (Valenciennes, 1846), the information was scarce on oxygen consumption. This study was to analyze the effect of stocking density on oxygen consumption in Barred loach conducted at Research Institute for Freshwater Aquaculture and Fisheries Extension, Bogor in May 2018. Barred loach (total length: 5.79 ± 0.47 cm, weight: 1.32 ± 0.34 g) was observed its oxygen consumption on three different stocking densities (5, 10, and 15 fish/L) by using closed respirometers (volume: 1.4 L) with three replications of each treatment. Measurement of oxygen consumption was carried out under normoxia and hypoxia conditions. In addition, fish behavior and ventilation rate were also observed and recorded according to treatment. The results showed that the highest oxygen consumption of barred loach was found in the stocking density of 5 fish/L (1250.6 ± 128.4 mg O2/kg/h) which was significantly different from the stocking density of 10 fish/L (626.9 ± 46.7 mg O2/kg/h) and 15 fish/L (596.9 ± 48.9 mg O2/kg/h). Meanwhile, oxygen consumption of barred loach under hypoxic conditions decreased significantly compared to normoxic conditions, which was marked by a decrease in their swimming activities. Although the ventilation rate in hypoxic conditions has decreased, the value was not significantly different from those of normoxia condition. Results of this study provide information that an increase in stocking density and hypoxic conditions in barred loach caused a decrease in oxygen consumption rates. In addition, this study showed that the critical oxygen level for barred loach was around 3.1 mg/L

<strong>Effect of Stocking Density on Oxygen Consumption and Stress Response in Crescent Betta (<em>Betta imbellis</em>)</strong>. Stocking density is one of the determinant parameters for fish growth optimization in aquaculture systems due to its relationship with fish metabolism. Information about the impact of different stocking densities on crescent betta (<em>Betta imbellis</em>) metabolism was not available yet. This study was aimed to analyze the effect of stocking density on oxygen consumption, critical oxygen level, and stress responses in crescent betta.The study was carried out under three different stocking density treatments: 5, 10, and 15 fish/L with three replications using 2.74 ± 0.23 cm total length and 0.22 ± 0.05 g body weight tested fishes.The parameters observed were oxygen consumption, ventilation rate, blood glucose level, cortisol, and critical oxygen level. The result showed that the highest oxygen consumption was found at 5 fish/L stocking density treatment (3.01 ± 0.28 mg O₂/g/h), which was significantly different from 10 fish/L (1.01 ± 0.21 mg O₂/g/h) and 15 fish/L (0.92 ± 0.08 mg O₂/g/h) stocking density treatments. Oxygen consumptions under hypoxic condition was not significantly different compared to normoxic condition.The ventilation rate tends to increase significantly along with the increasing of stocking densities. Critical oxygen levels were not significantly different among the treatments,with the value of 3.31 ± 0.65 mg/L, 3.14 ± 0.29 mg/L, and 2.83 ± 0.19 mg/L for stocking density of 5, 10, and 15 fish/L, respectively. The blood glucose level at 15 fish/L stocking density was significantly higher than others, whereas the cortisol levels was not significantly different among the treatments. The results of this study provided information that the increasing stocking density of cressent betta will decrease their metabolism activity and increase ventilation rate. However, the increase of ventilation rate was negatively correlated with oxygen consumption per breath at higher stocking densities due to decrease in fish activity; and higher stocking densities will decrease oxygen consumption. Based on the results, it can be concluded that the ideal stocking density for crescent betta is 5 fish/L. The increasing of stocking density will decrease oxygen consumption rates and increase the stress level of crescent betta.

Asian redtail catfish (Hemibagrus nemurus) is one of the economic freshwater fish species in Indonesia. There is still a lack of information regarding water quality tolerance of Asian redtail catfish. Therefore, this study was conducted to obtain information on the stress response of Asian redtail catfish under various pH exposures. The experimental fish was the second generation of domesticated Asian redtail catfish from the Cirata population (Length: 11.7 ± 0.6 cm; Weight: 13.2 ± 1.6 g). The pH treatment in this experiment was low pH (4-5), optimal pH (6-9), and high pH (10-11) with three replicates in each treatment. Stress response was observed by measuring blood glucose and plasma cortisol. Moreover, fish behavior and survival were also observed. Results showed that glucose level of Asian redtail catfish fingerlings was higher at low pH treatment (258.8 ± 75.1 mg/dL) than optimal (58.7 ± 7.5 mg/dL) and high pH treatment (151.0 ± 21.5 mg/dL) (P<0.05). Cortisol level at low (34.02 ± 3.16 IU) and high pH (32.88 ± 13.85 IU) was significantly higher than optimal pH treatment (12.56 ± 5.18 IU) (P<0.05). Low and high pH exposure to Asian redtail catfish increased their cortisol and glucose levels, which will lead them to mortality.